Field
The presently disclosed subject matter relates to a semiconductor light-emitting device having multiple light-emitting elements such as light-emitting diode (LED) elements arranged in a matrix.
Description of the Related Art
Generally, a semiconductor light-emitting device formed by LED elements arranged in a matrix including rows and columns has been used as a vehicle headlamp. In such a semiconductor light-emitting device, luminous intensities of the LED elements are individually controlled in real time to realize an adaptive drive beam (ADB) and an adaptive front-lighting system (AFS) (see: JP2013-54849A & JP2013-54956A).
In an ADB control, when a preceding vehicle including an oncoming vehicle is detected by a radar unit or the like, the luminous intensities of only the LED elements facing toward the preceding vehicle are decreased to decrease the illuminance toward the preceding vehicle while a high-beam mode is maintained. As a result, glare toward the preceding vehicle can be suppressed while the visibility in a high-beam mode can be maintained toward the preceding vehicle.
In an AFS control, when a steering angle read from a steering angle sensor or the like is larger than a predetermined value, the LED elements having high luminous intensities are shifted from a central area of the device to a right side or a left side of the device, to substantially decline the optical axis of the device while the visibility in a high-beam mode is maintained.
FIG. 1A is a plan view illustrating a first prior art semiconductor light-emitting device, as the above-mentioned device and FIG. 1B is a cross-sectional view taken along the line B-B in FIG. 1A. As illustrated in FIGS. 1A and 1B, this semiconductor light-emitting device includes a semiconductor wafer (body) 1 in which blue LED elements D11, D12, . . . , and D33 in three rows, three columns are formed. Also, a wavelength-converting layer 3 including a transparent resin layer 31 having yitrium aluminium garnet Y2Al5O12:Ce3+ (YAG) particles for wavelength-converting blue light into yellow light to form white light and barium-titanium-based particulate spacers 32 is formed on the LED elements D11, D12, . . . , and D33. Further, a support body 2 is provided to support the semiconductor body 1. In this case, the semiconductor body 1 is wafer-bonded onto the support body 2. This device further includes a transparent plate 4 to make the wavelength-converting layer 3 uniform.
Note that each of the LED elements D11, D12, . . . , and D33 is square or rectangular viewed from the top, so that the LED elements D11, D12, . . . , and D33 can be in close proximity to each other.
In the first prior art semiconductor light-emitting device of FIGS. 1A and 1B, since there are still relatively large spaces between the LED elements D11, D12, . . . , and D33, even when the LED elements D11, D12, and D33 are operated to emit lights L11, L12, . . . , and L33, respectively, as illustrated in FIG. 2A, dark regions DR forming a dark grid would be created at the spaces. As a result, as illustrated in FIG. 2B, light emitting regions ER21 and ER22 of the LED elements D21 and D22 would be decreased. In this case, the larger the spacing between the LED elements D11, D12, . . . , and D33, the larger the dark regions DR.
On the other hand, when the LED elements D11, D12, . . . , D33 are closer to each other as illustrated in FIGS. 3A and 3B, the dark regions DR would be reduced in size to increase the light emitting regions ER21 and ER22. In this case, however, when the LED elements D11, D12, D13, D21, D23, D31, D32, and D33 except for the LED element D22 are operated to emit lights L11, L12, L13, L21, L23, L31, L32, and L33, leakage lights LL would be leaked into the non-operated LED element D22 from its adjacent operated LED elements. Therefore, weak light would be emitted from the non-operated LED element D22, so that optical crosstalk would be generated between the non-operated LED element and its adjacent operated LED elements.
Thus, in the first prior art semiconductor light-emitting device of FIGS. 1A and 1B, it is preferable that both of the dark regions DR and the optical crosstalk be as small as possible; however, there is a tradeoff relationship between the dark regions DR and the optical crosstalk.
A second prior art semiconductor light-emitting device includes multiple light-emitting elements each with one wavelength-converting layer thereon on a support body, a grid-shaped optical shield wall for separating the multiple light-emitting elements from each other, multiple transparent plates each provided on one of the multiple light-emitting elements, and a grid-type optical shield frame for separating the transparent plates from each other (see: JP2013-187371A). Thus, both of the dark regions and the optical crosstalk can be decreased by the grid-shaped optical shield frame.
In the above-described second prior art semiconductor light-emitting device, however, since the thickness of the walls of the grid-type optical shield frame is actually very large, i.e., several tens of μ m, the dark regions are still very large. Also, the presence of the grid-shaped optical shield frame would increase the manufacturing cost.
A third prior art semiconductor light-emitting device includes multiple light-emitting elements on a support body, a grid-shaped optical shield frame having throughholes corresponding to the light-emitting elements on the support body, and multiple wavelength-converting filter plates each provided in one of the throughholes over one of the light-emitting elements (see: JP2009-134965A). Thus, both of the dark regions and the optical crosstalk can be decreased by the grid-shaped optical shield frame.
In the above-described third prior art semiconductor light-emitting device, however, since the thickness of the walls of the grid-shaped shield frame is actually very large, the dark portions are still very large. Also, the presence of the grid-shaped optical shield frame would increase the manufacturing cost.